Machines such as a tractors or bulldozers are equipped with attached implements for performing various tasks. For example, a tractor may be equipped with a blade for scraping the ground and pushing material. An operator can move the position of the blade up and down relative to the ground. This helps the tractor complete the task of properly leveling or contouring the ground on which the tractor is operating. This is a task often performed during the construction of roads, buildings, or other structures.
One difficulty facing a tractor is that the movement of the tractor over uneven terrain results in the blade pitching up or down as the tractor itself pitches up or down across the terrain. For example, if the tractor begins to climb over a bump, the front of the tractor will pitch up, resulting the tractor's blade also pitching up. The causes the blade to dig shallower than if the tractor were on level ground.
Conversely, if the front of the tractor pitches downward, the blade will also pitch downward. Unless the operator corrects for this movement, the pitching of the blade will result in the blade digging into the earth too deeply than is desired.
Operators of a tractor can correct for uneven terrain by adjusting the motion of the blade as the machine moves over uneven terrain. For example, if the operator perceives that the tractor is pitching or will pitch upward, the operator can command the blade to move downward to compensate for the tractor's movement, resulting in a smoother surface. However, the quality of the resulting grade is dependent on the skill of the operator in anticipating the need to adjust the blade. The operator may have to slow the speed of the machine in order to better adjust the blade in response to uneven terrain, which reduces the efficiency of the machine and may increase the cost of completing the work.
Systems and methods exist to automatically adjust the position of an implement, such as a blade on a tractor, to produce more uniform results. For example, systems may produce a map of the worksite with target finishes, which can be fed to sensors on the machine to automatically adjust the blade to produce a desired finish. These systems may produce desirable results, but may be very expensive. Also, the finished surface must often be defined accurately before work can begin, rather than allowing for adjustment that can be achieved as work at the site progresses. It is desirable to have a system that still produces a smoother finish than obtainable by operator adjustment alone, but does not require as much expensive equipment and control systems as in many prior art grading systems. The system should provide greater efficiency than no control on the machine.
U.S. Pat. No. 7,121,355 to Lumpkins et. al (“Lumpkins”) discloses a system for controlling the position of a machine blade for grading. In Lumpkins, a control system determines the difference between a target position of a blade and an actual position, and generates a control signal calculated to move the blade to the target position.
Although the system disclosed by Lumpkins purports to more accurately control the position of a blade, the Lumpkins system may not adequately compensate for the fact that the operator may be commanding the machine implement in anticipation of uneven terrain. The system disclosed by Lumpkins does not electronically attempt to discern a difference between when an operator is attempting to move the blade to a new target position, and when the operator is merely attempting to compensate for uneven terrain. Consequently, the Lumpkins system requires a separate lever that the operator controls, which alternately tells the system to return the blade to a target position, or tells the system that the operator is attempting to override the control system and move the blade to a new target position.
It is desirable to have a control system which is easier to operate, and which adjusts the implement rate of change on a machine in response to uneven terrain while recognizing that the operator may simultaneously be issuing implement commands which attempt to achieve the same intention as the control system. Moreover, it is desirable to have a machine implement control system that produces a smoother grade or contour without the necessity of knowing or calculating an actual target position for the implement.
The present disclosure is directed to overcoming or mitigating one or more of the problems set forth above.